The invention relates to a hydrodynamic converter with a torus-shaped working chamber, an impeller, a turbine wheel and a ring of adjustable guide vanes.
In particular, the invention relates to a converter for use in a machine set in which the drive is a gas turbine and the machine is a compressor. The power outputs here are extremely high, being of the order of 20 megawatts and above. Owing to these extreme power outputs, the machines also have extremely large revolving masses, which, by their very nature, lead in turn to special problems.
The requirements of a machine set of the stated type, especially one with a gas turbine and a compressor, are as follows:
the compressor must be started up without the drive being overloaded
the compressor must be run up to a speed that is equal to the speed of the drive, i.e. the two machines must run synchronously with one another
once synchronicity has been achieved, a direct mechanical drive connection must be established between the drive and the machine
in the case of many machine sets of the stated type, especially those comprising a gas turbine as a drive and a compressor as a machine, it may be necessary to have the gas turbine run continuously, even when the compressor is switched off.
In principle, a hydrodynamic converter would be suitable as an intermediate member between the gas turbine and the compressor. However, converters known hitherto are not capable of performing the functions mentioned, if only for reasons of strength. When they are partially filled, cavitation occurs owing to the high power outputs involved. When completely filled, a converter of the type stated cannot cope with the extreme power outputs required.
The object of the invention is to specify a hydrodynamic converter which is suitable, in particular, as an intermediate member between a gas turbine and a compressor. A converter of this kind should be able to transmit extremely high power outputs and effect synchronicity between the gas turbine and the compressor.
The object is achieved by the features of invention. The converter includes an input shaft on which an impeller is rotationally fixed, an output shaft on which a turbine wheel is rotationally fixed and the impeller and turbine wheel together define a torus shaped working chamber which surrounds the axis of the converter and the shafts. The torus shaped working chamber has the form of a ring channel when viewed in axial section. A ring of adjustable guide vanes is disposed in the working chamber. The impeller and the turbine have respective flow channels in the working chamber and working fluid flows around the ring channel, through the flow channels of the impeller and the turbine wheel and past the guide vanes. The converter is configured so that it has a lambda value of less than 0.005 and a speed ratio between the turbine wheel and the impeller on the order of one. As a result of the arrangement in placement of the flow channels of the impeller and the turbine, flow of working fluid through the flow channels of the impeller is essentially centrifugal, while flow of working fluid through the flow channels of the turbine wheel is essentially centripetal. The flow channels of the impeller and turbine wheel are so positioned that the leading edges of the impeller blades and the trailing edges of the turbine blades are closer to the converter axis than the other edges of the impeller blades and the turbine blades.
When the converter is used in a machine for high power output, there is in addition a separately operable tooth clutch connected in parallel with the converter with a clutch half rotationally fixed to each of the shafts and one of the clutch halves being moveable to selectively engage and disengage the clutch halves while both clutch halves remain rotationally fixed to the respective shafts.
In the past, the aim with hydrodynamic converters was to achieve a high xcex value in order to keep the overall volume of the converter small. Admittedly, an extremely small xcex value, of the order of 0.0005, is achieved with the configuration according to the invention. At the same time, the speed ratio v between the speed of the turbine wheel and that of the impeller is of the order of one. Efficiency is high. It is of the order of 0.75 and above.
With the configuration according to the invention, the flow through the channels of the impeller is essentially centrifugal. That through the channels of the turbine wheel is essentially centripetal, something that is unusual in the case of converters. Thanks to this configuration, extremely high power outputs can be transmitted with a moderate overall volume, a high efficiency and the ability to establish the synchronized condition.